Diffusive optical tomography (DOT) is a form of computer-generated tomography wherein near-infrared light (NIR) is directed at a biological object (e.g., a inclusion, tumor, and so forth) and the amount of light transmitted and/or diffused through the object, and/or reflected from the object, is detected and utilized to reconstruct a digital image of the target area (e.g., the object can exhibit a differential in transmission and/or diffusion from surrounding tissues). This method of imaging is of interest for several reasons, for example, differing soft tissues exhibit differing absorption, transmission and/or scattering of near-infrared light. Therefore, DOT is capable of differentiating between soft tissues, wherein alternative tomography methods (e.g., Positron Emission Tomography, Magnetic Resonance Imaging, X-Ray, and so forth) cannot. Another example is that near-infrared light is non-ionizing to bodily tissues, and therefore patients can be subjected to repeated light illumination without harm. This in turn allows physicians to increase the frequency at which they monitor and/or track changes in areas of interest (e.g., inclusions, tumors, and so forth). Yet further, due to differences at which natural chromophores (e.g., oxygen-hemoglobin) adsorb light, optical tomography is capable of supplying functional information such as hemoglobin concentration. For these reasons there is much interest in employing optical tomography for the detection and monitoring of soft tissues, especially in breast cancer applications.
Although diffusive optical tomography is a promising medical imaging technique, DOT imaging methods and DOT apparatus have yet to yield high quality reconstructions of inclusions due to fundamental issues with intense light scattering.
Another method of tomography imaging that is of interest is fluorescent diffusive optical tomography (FDOT). Fluorescent diffusive optical tomography is a form of computer-generated tomography wherein an excitation source (e.g., near-infrared light) is directed at a biological object labeled by a dye fluorophore. Upon excitation of the fluorophore, the wavelength of the excitation source is shifted to a differing wavelength (e.g., a Stokes-shift) as it is emitted by the fluorophore. The emitted light is then detected and utilized to reconstruct a digital image of the target area, which can exhibit a differential in fluorophore concentration from surrounding tissues (e.g., fluorophore take-up). The digital image can be employed to provide functional characteristics about the biological object, such as vascular endothelial growth factor (VEGF). However, FDOT methods have exhibited less than desirable reconstruction accuracy due to imperfect uptake of the fluorophore and background fluorophore noise.
Diffusive optical tomography and fluorescent diffusive optical tomography individually provide benefits over alternative imaging methods. Each of these imaging methods is confronted with challenges that impede widespread acceptance and implementation. However, an optical tomography system capable of providing high quality images of soft tissue to enable physicians to monitor soft tissues with greater frequency, and capable of providing functional characteristics about a portion of biological tissue imaged, would be desirable.